1. Field of the Invention
This invention relates to a solid state imaging apparatus, wherein solid state imaging devices such as COD (charge-coupled device) imagers are employed.
2. Brief Description of the Prior Art
Recently, the development of solid state television cameras has been very active. They employ solid state imaging devices such as photo-diode arrays, CCD imagers, BBD (bucket brigade device) imagers, and so on, instead of vidicon tubes. These solid state imaging devices have limited number of picture elements, therefore, it is very difficult to improve resolution of an image. If a plurality of imaging devices are employed in one camera system, the resolution of picked up images can be improved by suitable displacement of imagers and signal processings as shown in U.S. Pat. No. 3,975,760, which was assigned to the same assignee as the present application.
That is, three imaging chips or devices 1G, 1R and 1B are disposed with respect to a single focused image as shown in FIG. 1. In this case, with the focused image on the imaging device 1G being as a reference, the imaging device 1R is shifted therefrom in the horizontal direction by a distance corresponding to a phase .theta..sub.12 and the imaging device 1b is shifted therefrom in the horizontal direction by a distance corresponding to a phase .theta..sub.13. FIG. 1 is an example such as being arranged as a color camera system and hence color filters FR, FB and FG (not shown) are respectively disposed in front of the corresponding imaging devices 1R, 1B and 1G. Accordingly, a signal corresponding to red color is obtained from the imaging device 1R, and similarly a signal corresponding to blue color from the imaging device 1B and a signal corresponding to green color from the imaging device 1G, respectively.
In FIG. 1, if the alignment pitch of horizontally arranged picture elements 2 is taken as x and scanning time of this pitch x is .tau..sub.H, sampling frequency f.sub.c for the focused image can be expressed as f.sub.c =1/.tau..sub.H. In FIG. 1, y indicates an aperture width of each picture element 2, and .tau..sub.0 a scanning time of this aperture width y. Further, the phases .theta..sub.12 and .theta..sub.13 correspond to the distance of 1/3 x and 2/3 x, respectively.
In the case that the spatial positioning of the focused image and the imaging devices is selected in a manner as mentioned above, if the respective imaging devices 1G, 1R and 1B are read out at proper sampling timings corresponding to the above positioning, the output levels and the phase relation as shown in FIG. 2 are obtained. FIG. 2 shows levels and phase relation of respective components of a composite output, in which Y.sub.B designates a base-band component and Y.sub.S a side-band component. Carriers of the side-band component Y.sub.S (sampling pulses) C.sub.G, C.sub.R and C.sub.B have phase relation as shown in FIG. 2. It is assumed that the spatial phase relation can be correctly selected as .theta..sub.12 =2/3.pi. and .theta..sub.13 =4/3.pi.. In this case, upon picking up a black and white image, if outputs of three imaging devices are added together with their levels being made equal so as to produce a luminance signal, the side-band components Y.sub.S are cancelled by taking vector sums, while only the base-band components Y.sub.B remain.
As described above, when the alignment adjustment among the devices 1G, 1R and 1B is perfect, the side-band components are cancelled out so that a desired aim can be achieved. Meanwhile, if the alignment adjustment is imperfect, the side-band components are not cancelled but remain in the base-band components Y.sub.B. Therefore, the quality of pictures can not be improved and also the frequency band can not be widened. As a matter of fact, however, each imaging device is small in size. Besides, with a device incorporated with several hundreds of picture elements in the horizontal direction, it is quite difficult to correctly provide a mechanical positioning corresponding to a time 1/3.tau..sub.H.